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MONDAY, June 30, 2003 (HealthDayNews) -- Obesity raises the risk of death from colon cancer in women, but not men.
That's the surprising conclusion of a new study that found female colon cancer patients can expect a much worse outcome if they're heavy, and perhaps even a greater chance their tumors will return. But the study, reported in the August issue of Cancer, found no such association in men, whose outcomes were unaffected by their weight.
Previous studies have found obesity's impact on developing colon cancer and dying from it is stronger in men than in women, says Eugenia Calle, an epidemiologist at the American Cancer Society. "It's one of the most consistently observed gender differences," Calle adds.
However, the latest work focused on people who'd already been diagnosed with colon tumors, not the incidence of the disease in the general population, which could help explain the difference.
What's not in dispute is the overall connection between weight and cancer. Earlier this year, Calle and her colleagues reported that overweight and obesity could account for as many as one in seven cancer deaths among men, and one in five among women, each year in the United States.
Being overweight increases blood levels of certain hormones and proteins, such as estrogen and insulin, which can stimulate tumors. Weight affects the risk of cancers in both sex-neutral organs, such as the esophagus, colon, liver and gallbladder, as well as sex-specific sites such as the breast, ovaries, cervix in women and the prostate gland in men.
In the latest study, Dr. Jeffrey Meyerhardt, of the Dana-Farber Cancer Institute in Boston, and his colleagues looked at the link between body mass index -- a ratio of height and weight -- and colon cancer in 3,759 men and women who'd been diagnosed with the disease. All the patients were enrolled in a clinical trial of a now-common drug taken after surgery to reduce the risk of relapse.
Obese women -- those with a BMI was at least 30 -- were about a third more likely than their normal-weight peers to die within roughly nine years of starting the study. They also appeared to be somewhat more likely to suffer relapses of their cancer, although the study wasn't large enough to prove that.
Weight wasn't a factor in survival or return tumors for men, the researchers found.
For patients of either gender, being overweight did seem to provide at least one benefit. Obese patients were less likely than their thinner counterparts to suffer serious side effects from their chemotherapy.
Although many cancer drugs are given in proportion to a patient's "ideal" weight, the doses in the latest study were based on actual weight. The results therefore suggest "that we should be treating patients doses based on their actual body weight," Meyerhardt says.
It's possible, he adds, that the fewer side effects in the overweight patients is a signal that higher doses of cancer drugs could be used safely and with better results.
Previous research has hinted that women who gain significant amounts of weight in the year after being diagnosed with breast cancer face a worse prognosis than those who stay the same weight. Researchers at Dana-Farber are now looking at whether the same phenomenon occurs in colon cancer patients.
Colorectal cancer will be diagnosed in more than 147,000 Americans this year, and more than 57,000 will die from the disease, according to the American Cancer Society.